What is the dose of Enoxaparin (Low Molecular Weight Heparin) for Myocardial Infarction (MI)?

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Last updated: May 17, 2025 • View editorial policy

From the Guidelines

For patients with myocardial infarction (MI), the recommended dose of enoxaparin is 1 mg/kg administered subcutaneously every 12 hours, as indicated in the 2025 ACC/AHA/ACEP/NAEMSP/SCAI guideline for the management of patients with acute coronary syndromes 1.

Key Considerations

  • The dose should be reduced to 1 mg/kg once daily for patients with significant renal impairment (creatinine clearance <30 mL/min) 1.
  • An initial intravenous bolus of 30 mg may be given before starting the subcutaneous regimen in ST-elevation MI (STEMI) cases, but this is not recommended for patients over 75 years old 1.
  • Treatment typically continues for the duration of hospitalization, usually 2-8 days, or until revascularization occurs.

Mechanism of Action

  • Enoxaparin works by inhibiting factor Xa and thrombin, preventing clot formation and extension.

Monitoring and Safety

  • Regular monitoring of anti-Xa levels is not routinely required, but may be considered in patients with renal impairment, obesity, or pregnancy.
  • Watch for bleeding complications and adjust dosing based on patient-specific factors.

Comparison with Other Anticoagulants

  • The choice of anticoagulant should be based on individual patient factors, including renal function and the need for invasive procedures 1.
  • Fondaparinux and bivalirudin are alternative anticoagulants that may be considered in certain situations, but their use is guided by specific clinical scenarios and patient characteristics 1.

From the Research

Enoxaparin Dosing for MI

  • The dosing of Enoxaparin for patients with myocardial infarction (MI) has been studied in several trials 2, 3, 4, 5, 6.
  • In the STEEPLE trial, patients received a bolus of intravenous enoxaparin (0.5 or 0.75 mg/kg) 2.
  • The ExTRACT-TIMI 25 trial used an initial 30 mg intravenous bolus of enoxaparin, followed by 1 mg/kg subcutaneously within 15 minutes and then every 12 hours for up to 8 days 3, 4.
  • For patients > 75 years of age, the initial bolus of enoxaparin was not given, and the 12-hourly dosages were reduced to 0.75 mg/kg 3, 4.
  • In patients with an estimated creatinine clearance of < 30 mL/min, the dose was reduced to 1 mg/kg every 24 hours 3, 4.
  • The TIMI 11A trial compared two weight-adjusted regimens of subcutaneous injections of enoxaparin (1.25 mg/kg or 1.0 mg/kg every 12 hours) 5.
  • The TIMI 11B trial used an initial 30 mg intravenous bolus of enoxaparin, followed by injections of 1.0 mg/kg every 12 hours 6.

Special Considerations

  • Patients with renal impairment may require dose adjustments, but the STEEPLE trial found that enoxaparin can be administered safely without dose adjustment in these patients 2.
  • Patients > 75 years of age may require reduced dosages 3, 4.
  • Patients with an estimated creatinine clearance of < 30 mL/min may require reduced dosages 3, 4.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.